It is known in the art to use capping devices for applying threaded caps to pre-threaded containers. Such devices utilize a clutch to control the amount of torque applied to the cap so that the container is properly closed but prevents too much torque from being applied that could strip the threads of the container and the cap. Also, it is desired to prevent the over tightening of the cap.
This has been accomplished by using rings of concentric magnets with some form of control to control the axial position of the magnets. Various devices have also incorporated rings of magnets of alternating polarity. Even though such devices have been available, they have tended to be complex and costly, and not very reliable with regard to retaining the pre set torque, and thus many capping devices utilizing spring loaded mechanical and friction clutches are still in use but a need exists for a device incorporating a reliable and simplified but effective clutch mechanism.
One such device can be found in U.S. Pat. No. 5,197,258, issued Mar. 30, 1993 to Johanek in which a clutch is adapted for use in a capping device to apply a pre-selected amount of torque to the driven component having a pair of axially aligned circular cylinders of equal diameter each having a generally smooth engaging surface facing the other clutch cylinder. Each of the cylinders has cavities in the rear side for containing magnets. The magnets are secured in the cavities by means of a cured polymeric resin. The maximum torque provided by the clutch is controlled by using removable spacer disks of varying thicknesses and having a diameter equal to that of the cylinder positioned between the engaging surfaces.
The device disclosed in U.S. Pat. No. 5,437,139, issued on Aug. 1, 1995 to Martin deals with a cylindrical magnet ring in the body of the head surrounding a cap chuck driving element in a low friction bearing in the head, each having an array of permanent magnets, distributed around the periphery. The chuck driving element rotates with the magnet ring until the resistance of a cap being threaded on the container exceeds a predetermined torque limit, after which the magnet ring rotates relative to the stationary chuck driving element. The spring for urging the chuck downward is fully contained within the head.
Yet another device is that found in U.S. Pat. No. 5,809,742, that issued on Sep. 22, 1998 to Takakusaki, et al in which a plurality of permanent magnets are embedded around the entire outer periphery at the upper end of a spindle with adjacent permanent magnets presenting magnetic poles of different polarities. As the capping head moves through a threadable engaging zone, co action between the permanent magnets causes the capping head to rotate clockwise causing a cap to be threadably engaged with a container.
U.S. Pat. No. 5,714,820, that issued on Feb. 3, 1998 to Mitsuhashi, et al deals with magnetic coupling that includes a cylindrical housing, a spindle, an adjusting plate, two pairs of permanent magnet discs, two hysteresis material discs, and a screw member.
The spindle is rotatably supported at its axial position by the housing. The adjusting plate is rotatably supported by the spindle to partition as interior of the housing into two sections in a direction of the spindle. The two pairs of permanent magnets are provided in the two corresponding section to respectively oppose each other. One of each pair of permanent magnet discs is fixed in the housing and the other thereof is fixed to the adjusting plate. Each permanent magnet disc has magnetic poles with polarities that alternate in a circumferential direction. The hysteresis material discs are fixed to the spindle and arranged between the corresponding pairs of permanent magnet discs at a predetermined gap. The screw member fixes the adjusting plate to the housing. When the adjusting plate is released and pivoted, the mutual positional relationships between the respective opposing magnetic poles of the two pairs of permanent magnet discs are adjusted simultaneously.
U.S. Pat. No. 6,240,678 that issued Jun. 5, 2001 to Spether, deals with a capping head assembly that has a first housing with a spindle mounting collar and supports a clutch housing. The clutch housing has an upper portion with a first magnetic ring and a lower portion with a second magnetic ring. The lower portion is freely rotatable relative to the upper portion and permits the adjustment of the air gap between the first and second magnetic rings. A locking mechanism maintains the adjusted air gap at a selected value that represents a definable torque level in the magnetic clutch. The capping head also includes a post assembly calibration system that establishes a known reference point. that compensates for manufacturing tolerances between individual capping heads.
There is disclosed in U.S. Pat. No. 5,490,369, that issued Feb. 13, 1996, to Ellis, a capping head with magnetic clutch that includes a housing assembly including a magnetic clutch interconnecting a drive spindle and a quill for applying a closure to a container. The magnetic clutch consists of opposed rings of magnets and one of the rings is disposed in a piston ring assembly that is quick and easily adjustable relative to the other to vary the torque limit of the clutch. A simple yet efficient clamping assembly is employed to facilitate ready adjustment and retention of the movable piston ring.
There is shown in an Arol Company brochure, not dated, a synchronous magnetic type of head. This device differs from the device herein by the use of straight sided ball bearings as the contact thrust bearing, but more importantly, it uses a synchronous magnetic type of head as opposed to the hysteresis type of head as used in the inventive device herein.
Basically, the synchronous clutch utilizes two discs with multiple magnets that are set up to oppose each other. To rotate one of the discs relative to the other disc you must overcome the magnetic attraction from the north pole to the south pole. The torque is a pulsating torque from zero to maximum. The number of magnets located around the disc will determine how many pulsations there will be in one revolution. To change peak torque levels in this type of design you need to adjust the air gap between the magnets. Larger air gaps provide for smaller peak torques.
In the hysteresis clutch of the instant invention, the action is smooth. That is the primary benefit that the inventive device incorporates. The device has three magnet plates, not two. The hysteresis magnet is sandwiched between two multiple pole driver magnets. By varying the polar orientation of the driver magnets the magnetic saturation of the hysteresis magnet can be changed. A fully saturated magnet makes full torque and it is a smooth constant torque, not a pulsating torque. One need not deal with the air gap between the magnets in this type of device.
None of the devices disclosed in the prior art have the advantages of the device of the instant invention. None of the devices disclosed in the prior art have the simplicity and novel means of adjusting the torque in the magnetic clutch assembly as does the device of the instant invention. In addition, none of the devices of the prior art have the capability of being able to read the adjustments scale on the outside surface of the magnetic clutch assembly, nor the adjustments scale on the outside surface of the upper spring assembly for adjusting the tension in the spring.
The device of the instant invention does not rely on the gap between magnets for adjusting the torque therein.